A roller transportation device can be used for transporting an article. The roller transportation device has one or more roller drives. The roller drive has an electric motor for driving the roller. The electric motor is either an external or else an internal rotor. Roller transportation devices have multifarious applications. Areas of application include baggage conveyors at an airport, parcel conveyors in a mail-distribution center, and material or bulk conveyors in production facilities or warehouse stores, etc. An article is transported by means in particular of a combination of roller drives and passive rollers, both of which are rollers. Passive rollers have no electric motor but can nonetheless be co-moved by the roller drives by means of, for instance, a transmission belt. A roller drive is an active roller.
The electric motor can be operated by means particularly of drive electronics. Said drive electronics include in particular regulating electronics and power electronics. The drive electronics can be driven by a superordinate control means. A serial bus system, for example, is used for driving.
All manner of problems arise when roller drives and roller transportation systems are in use. For example the greater the number of parts required for operating the roller drive is, the longer they will take to assemble. That is disadvantageous in terms particularly of replacement parts, meaning when a defective roller drive is being replaced.
The roller drives' electric power causes heat to develop. Depending on the specific application, the temperature of the roller drive often must not exceed a specified maximum temperature. Particular importance therefore attaches to cooling the roller drive. Said cooling therein relates to maintaining not only application-specific maximum temperatures but also maximum temperatures dictated by the electric motor itself or by its drive electronics. To avoid exceeding all maximum temperatures it is possible to distribute a roller's electric power between/among two or more roller drives. That, though, has the disadvantage that more roller drives will be needed and that the cabling and connection requirements for the roller drives will increase. The use of a plurality of roller drives is usually associated with increased space requirements.
Another problem associated with rollers that have integrated roller motors is that they heat up. A modular and compact design basically yields cost advantages in setting up roller and belt transportation systems because of shorter on-site assembly times. The transportation system's drive can, as is known, be implemented modularly if the motors are arranged as what are termed roller motors inside the rollers. That, though, causes the cited heating-up of the rollers.
The roller drive has a roller whose surface is as a rule not touch-guarded. That means that according to applicable regulations a temperature of around 75° C. must not be exceeded. The heat-transfer coefficient from the roller's surface to its ambient region is, however, relatively small. The consequent low dissipation of heat to the ambient region is for roller motors a limiting variable for the continuous torque. In resolving said heat-related problem it is necessary always to consider further central requirements placed on roller drives consisting in implementing a very small structural space and insuring as much possible freedom from maintenance as possible.
The reason why the cabling effort associated with roller drives is high is because they are produced in a structural unit providing one or more connecting cables for connecting the roller drive. It is thus necessary, for example, to duct a connecting cable's connecting leads through an axle of the respective electric motor. Threading the leads through is, though, again associated with a relatively large assembling effort.
A roller conveyor's rollers are usually mounted in a conveyor frame's side cheeks directly in accommodating openings in long sides of said frame. The roller conveyor is a roller transportation device. In contrast to non-driven (passive) rollers it is necessary when using roller drives, meaning rollers having an integrated electric motor that is an electric machine, to take up the driving motor torque of the motor integrated in the roller body and brace it against the frame of the roller transportation device, thus in particular against at least one side cheek.
It is known how to embody axle ends of roller drives as being profiled in cross-section, for example as a square or hexagon that is inserted into a correspondingly shaped accommodating opening on the conveyor's frame and so able to take up the torque. Increasingly greater requirements have to be placed on profiling when torques are large. A roller drive of said type is known from, for example, EP 1 209 101 A1.